page_title: Edmontosaurus annectens
section_title: Classification
hierarchical_section_title: Edmontosaurus annectens / Classification
caption_attribution_description: English: Compilation of virtually all known complete edmontosaur skulls from North America. All skulls are in lateral view (sometimes reversed). Labels below each skull include the symbol used in the morphometric plots, whether the specimen represents a holotype (type), the formation where it was uncovered (HCF, Horseshoe Canyon Formation; HF, Hell Creek Formation; FF, Frenchman Formation; LF, Lance Formation), and the species name based on traditional edmontosaur taxonomy. Scale bar, 20 cm. Deutsch: Fototafel mit faktisch allen vollständig erhaltenen „Edmontosaurier“-Schädeln. Alle Schädel sind in Seitenansicht (zur besseren Vergleichbarkeit teilweise gespiegelt). Die Beschriftungen unterhalb der Schädel bestehen aus dem Symbol, das in den morphometrischen Diagrammen verwendet wird (im entspr. PLoS-Artikel), aus der Exemplarnummer, ggf. aus der Angabe, dass es sich um ein Typusexemplar handelt, aus einem Kürzel, das für die Formation steht, aus der das entsprechende Stück stammt (HCF, Horseshoe-Canyon-Formation; HF, Hell-Creek-Formation; FF, Frenchman-Formation; LF, Lance-Formation) sowie aus dem Namen des Taxons, dem die Stücke traditionell zugeordnet werden. Die Länge des Maßstabsbalkens beträgt 20 cm.
context_page_description: Edmontosaurus annectens is a species of flat-headed and duck-billed dinosaur from the very end of the Cretaceous Period, in what is now North America. Remains of E. annectens have been preserved in the Frenchman, Hell Creek, and Lance Formations. All of these formations are dated to the late Maastrichtian stage of the Late Cretaceous Period, representing the last three million years before the extinction of the dinosaurs. Also, E. annectens is also from the Laramie Formation, and magnetostratigraphy suggests an age of 69-68 Ma for the Laramie Formation. Edmontosaurus annectens is known from numerous specimens, including at least twenty partial to complete skulls, discovered in the U.S. states of Montana, South Dakota, North Dakota, Wyoming and Colorado and the Canadian province of Saskatchewan. It was a large animal, up to approximately 12 metres, potentially up to 15 m in length, with an extremely long and low skull. E. annectens exhibits one of the most striking examples of the "duckbill" snout common to hadrosaurs.
context_section_description: E. annectens was a saurolophine or "flat-headed" hadrosaurid; this group was historically known as Hadrosaurinae. Species now considered to be synonyms of Edmontosaurus annectens were long recognized as closely related to both the genus and the species. However, the skull of the sub-adult type specimen of E. annectens differs noticeably from fully mature remains, so many researchers had classified the two growth stages as different species or even genera. On the other side of the issue, other authors, from John Bell Hatcher in 1902, to Jack Horner, David B. Weishampel, and Catherine Forster in 2004, and most recently Nicolás Campione and David Evans, have proposed that the large, flat-headed specimens most recently classified as Anatotitan copei belong to E. annectens.
  E. annectens was also historically classified in an independent genus, Anatosaurus, following the influential 1942 revision of Hadrosauridae by Richard Swann Lull and Nelda Wright, until it was reclassified as a species of Edmontosaurus by Michael K. Brett-Surman. With the discovery that A. copei and E. annectens likely represent the same species, some paleontologists have proposed using Anatosaurus as a valid genus name for E. annectens.
  The cladogram below follows Godefroit et al. (2012) analysis.
caption: Most known complete Edmontosaurus skulls (E. annectens from lower middle to right)
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